A4 Refereed article in a conference publication
Subshifts, MSO Logic, and Collapsing Hierarchies
Authors: Ilkka Törmä
Editors: Josep Diaz, Ivan Lanese, Davide Sangiorgi
Conference name: IFIP international conference on theoretical computer science
Publishing place: Berlin
Publication year: 2014
Journal: Lecture Notes in Computer Science
Book title : Theoretical Computer Science
Series title: Lecture Notes in Computer Science
Number in series: 8705
Volume: 1
First page : 111
Last page: 122
ISSN: 0302-9743
DOI: https://doi.org/10.1007/978-3-662-44602-7_10(external)
Web address : http://link.springer.com/chapter/10.1007/978-3-662-44602-7_10(external)
We use monadic second-order logic to define two-dimensional subshifts, or sets of colorings of the infinite plane. We present a natural family of quantifier alternation hierarchies, and show that they all collapse to the third level. In particular, this solves an open problem of [Jeandel & Theyssier 2013]. The results are in stark contrast with picture languages, where such hierarchies are usually infinite.
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